Studies are ongoing to evaluate in intact unanesthetized dogs the relationship between regional myocardial blood flow and regional myocardial infarction and the direct effects of acutely injured myocardium or tissue perfusion. These models are also being used to examine the relationship between regional blood flow and other indices of myocardial ischemic injury, i.e., ST segment changes and serum CK changes. Studies are ongoing to evaluate interventions which may alter the extent of myocardial injury and to determine whether local alterations in tissue perfusion are responses to reversible cellular injury.